Tactical military and commercial applications require self-organizing, wireless networks that can operate in dynamic environments and provide peer-to-peer, multi-hop, multi-media communications. Key to this technology is the ability of neighboring nodes to transmit without interference. Neighboring nodes transmit without interference by choosing time slots and channels that do not cause collisions at the intended unicast or multicast receivers. This functionality is provided by the Unifying Slot Assignment Protocol (USAP) which is the subject of U.S. Pat. No. 5,719,868, the disclosure of which is herein incorporated by reference. The function of USAP is to monitor the RF environment and allocate the channel resources on demand and automatically detect and resolve contention resulting from changes in connectivity.
A structured wireless channel access scheme such as Time Division Multiple Access (TDMA) may be used in an ad hoc wireless network. TDMA is a channel access technique in which a frequency channel is divided into time slots and each time slot is assigned to a user. Accordingly, multiple transmissions may be supported on a single frequency channel. In particular, a multi-frequency (or multi-channel) time division multiple access format such as Orthogonal Domain Multiple Access (ODMA) may be utilized. Multi-channel time-division multiple access is the subject of U.S. Pat. Nos. 5,949,760; 6,317,436; 6,331,973; 6,487,186; 6,504,829; 6,515,973; 6,574,199; 6,574,206; 6,600,754; 6,628,636 and 6,711,177, the disclosures of which are herein incorporated by reference.
A wireless communications network may include advantaged nodes which have enhanced visibility or connectivity to other nodes in the network. An example of an advantaged node is an airborne node such as an airplane flying over a battlefield. An advantaged node may be on other platforms such as s land-based platform, a space-based platform, a naval-based platform, etc. A non-advantaged node, e.g., a ground node, in a network may only have a small number of one-hop neighbor ground nodes due to the presence of hills, buildings and other terrain that may limit the RF connectivity between non-advantaged nodes. Non-advantaged nodes may be on other platforms such as a space-based platform, a naval-based platform, an air-based platform, etc. An advantaged node (e.g., an airplane node), however, is not hindered by such terrain and may, therefore, have a larger number of one-hop neighbor nodes than a non-advantaged node.
Congestion at the routing layer at an advantaged node may occur due to high demand by the non-advantaged nodes to use the advantaged node as a relay node to communicate with other non-advantaged nodes. In addition, congestion at the multiple-access layer (MAC layer) may also occur when too many non-advantaged nodes contend for access to the advantaged node at the same time. One solution to the problem of congestion at the MAC layer is to allow only a limited number of designated non-advantaged nodes, or access points, to send traffic to and receive traffic from an advantaged node. Accordingly, an access point exchanges traffic with other non-advantaged nodes as well as advantaged nodes. Typically, advantaged nodes are assigned to a separate physical channel (e.g., a separate RF channel) than the non-advantaged nodes. Therefore, an access point is required to participate on both the non-advantaged node channels and the advantaged node channel.
Accordingly, there is a need for system and method that allows a node, for example, an access point, in a wireless communication network to access multiple channels. In particular, there is a need for a system and method that allows a node to fully participate in the exchange of local time slot information on multiple channels. Further, there is a need for a system and method that allows an access point (e.g., a non-advantaged node) to fully participate in the exchange of local time slot information on the access points' channel and an advantaged node's channel.